@Mohsen certainly the drag model has not been properly coded meaning the results obtained in the paper are questionable. Did the authors of the paper use the same code? If so bring it to their attention that the code has some errors! i.e. the definition of the particle reynolds number is not correct and the condition for switching to different regimes is missing.

aoa, i have used this udf for gas solid fluidized bed and gives accurate results now i want to change from gas to liquid(water), tell me what are the changes required to do in code for this, waiting for ur reply
udf for customizing syamlal drag law in Fluent

i have used this udf for gas solid fluidized bed and gives accurate results now i want to change from gas to liquid(water), tell me what are the changes required to do in code for this, waiting for ur reply
udf for customizing syamlal drag law in Fluent